Conveyors of the type to which the present invention relate typically convey loads on the load carrying rollers at a higher speed than the speed of the chain itself, and at the same time run only the chain with the loads held on the rollers when required. The systems usually include chain covers covering sideways the inner and outer link plates and the traveling rollers of the conveyor chain.
This type of chain conveyor system is capable of conveying articles on the loading rollers at a higher speed then the traveling speed of the chain itself and, if need be, can cause the articles to dwell and permit only the chain to travel. This feature is used to accumulate articles. These conveyor chains are often utilized for load carrying and assembly operations. However, it has been found that in conveyors of this general type, foreign matter, such as a bolt or nut if loosened during an assembling operation, will be entrained or caught in the chain, and that when this happens damage to the rollers is possible and this may cause shutdown of the conveyor. For this reason, these conveyors have been fitted with protective covers to prevent damage to the rollers and shutdown of the conveyor due to entrainment of foreign matter.
One such prior cover is disclosed in Japanese Utility Model 197610/1987. FIGS. 12 and 13 show the details of this cover. The cover is generally designated by the numeral 50 and is of a flat plate type formed integrally with the link plates 52 and 54 which connect adjacent links. This cover has certain disadvantages and drawbacks. For example, since the cover 50 is of a flat plate type, there is a gap between the cover and the running roller 58. Foreign matter, such as a nut or bolt, may drop into the chain through this gap and thus the cover 50 does not truly function to prevent damage to the rollers, and stoppage of the chain under all operating conditions. Further the cover 50 is located radially outwardly of the outer diameter of the small diameter running roller 58. Thus, the small diameter running roller 58 cannot be received by a rail on the return side of the chain. Consequently, a large diameter load carrying roller 56 runs on the rail. Therefore, abrasion powder present on the rail adheres to the load carrying roller 56, the carrying side of the chain, and adheres to the load being carried.
Furthermore, even though chain cover 60 covers the chain and is utilized to prevent entrance of foreign matter, it has been found that dust which deposits on the cover 50 migrates into the chain without any resistance through the space between the cover 50 and each chain cover 60.
Moreover, on the return side of the chain, the load carrying roller 56 travels on the rail and this adversely effects the stability of the chain as compared with the running roller 58 riding on the rail.